Resin adhesive composition and laminated structure utilizing the same



United States Patent O 3,515,630 RESIN ADHESIVE COMPOSITION AND LAMI-NA'I'ED STRUCTURE UTILIZING THE SAME Peter S. Columbus, Whitestone, andRonald T. Mason,

New York, N.Y., assignors to Borden, Inc., a corporation of New JerseyNo Drawing. Filed Aug. 4, 1965, Ser. No. 477,293 Int. Cl. B32b 27/08,27/10, 27/30 US. Cl. 161-445 5 Claims ABSTRACT OF THE DISCLOSURE Thisinvention relates to an adhesive composition comprising (1) aninterpolymer of vinyl acetate with a C C ester of an acid selected fromthe group consisting of fumaric, maleic, acrylic acids and mixturesthereof, and to based on total weight of interpolymer, of apolymerizable monomer selected from the group consisting of ethenoidbond containing carboxylic acids, acid amides, and mixtures thereof; (2)a starch component selected from the group consisting of waxy starches,hydroxyalkyl starch ethers, acid modified starches, oxidized starches,and dextrines, and (3) a plasticizer for said interpolymer, there being,on a solids basis, about four parts of interpolymer and plasticizercombined for each part of the starch component; and to laminates madewith such adhesives.

Present day techniques require the use of high speed machines toautomatically apply and fasten labels to a variety of containers. Suchmachinery requires adhesives that must have a combination of properties.They must have (1) high initial tack in order to pick labels from thelabel bins and hold the label firm once applied to the container, and(2) lay-flat properties; i.e., will not blister but will cause the labelto remain flat and smooth. In addition, the adhesives must be stableunder the conditions of use and have clean machining properties. Thislatter characteristic is very important in automatic labeling equipmentsince adhesives now in use build up on the rollers and label picker armsnecessitating shut down of the machinery for cleaning. While presentlyavailable jelly gums and resin adhesives exhibit varying degrees ofthese characteristics and are generally suitable for labeling manymaterials, they are inadequate for use in labeling plastic containersand, in particular, polyvinyl chloride and polystyrene containers. Themain defects of such existing resin adhesives is their lack of initialtack, lack of clean machining properties, and high cost. Also, the jellygums give very poor final adhesion to these plastic surfaces.

It has now been found that resin labeling adhesives can be preparedwhich have excellent adhesion to plastics while at the same time havingthe high initial tack, clean machining properties required for use inpresent labeling apparatus.

Briefly stated, the present invention is directed to a resin adhesivecomprising a vinyl acetate interpolymer, a starch component, and aplasticizer for said interpolymer, there being, on a solids basis, aboutfour parts of interpolymer and plasticizer for each part of the starchcomponent, and to laminated structures utilizing said adhesive.

As to materials, the vinyl acetate interpolymer is suitably aninterpolymer of vinyl acetate with a C -C alkyl ester of fumaric, maleicor acrylic acids, and 0 to about 5% by weight, based on the total weightof the interpolymer, of a polymerizable monomer selected from the groupconsisting of ethenoid bond containing carboxylic acids, acid amides andmixtures thereof. Suitable esters are dibutyl maleate, dioctyl maleate,Z-ethylhexyl acryl- 3,515,630 Patented June 2, 1970 ate, ethyl acrylate,diethyl fumarate, dipropyl fumarate, dioctyl fumarate and mixturesthereof. Examples of such polymerizable monomers are acrylic acid,methacrylic acid, itaconic acid, crotonic' acid, citraconic acid, maleicaid, fumaric acid, acrylamide, and methacrylamide.

Specific examples of suitable interpolymers are those formed bypolymerizing parts of vinyl acetate with 25 parts of 2-ethylhexylacrylate; 74 parts of vinyl acetate with 24 parts of Z-ethylhexylacrylate and 2 parts itaconic acid; and those formed by polymerizing65-75 parts of vinyl acetate with 25-35 parts dioctyl maleate and A: to1 /2 parts of a mixture of acrylic acid and acrylamide. The method ofmaking such interpolymers can be any of the usual procedures known tothose skilled in the resin art and does not form any part of the instantinvention.

As to the proportions, suitable are 35-55 parts and for most purposesabout 40-50 parts of said ester for of the vinyl acetate.

The starch component used is preferably waxy milo starch (sorghumstarch). Waxy corn, tapioca, rice, and wheat starch can also be used,but are not as suitable. Other suitable starch components arehydroxyalkyl starch ethers, such as hydroxyethyl cornstarch ethers;oxidized starches, such as oxidized cornstarch and tapioca starch;acid-modified cornstarch, sorghum starch and tapioca starch; anddextrines, such as corn, tapioca, rice, potato, wheat, and sorghumdextrines. The dextrines while operative are the least suitable of theforegoing because of their relative lack of compatibility with the vinylacetate interpolymrs and they give a poorer adhesive tensile strength.

The plasticizers that may be used are those that are substantiallynon-volatile liquid ester solvents for the vinyl acetate interpolymers.Suitable examples are dipropylene glycol dibenzoate; triacetin,chlorinated biphenyls and polyphenyls; dibutyl, diethyl, dimethyl,diisobutyl, butylbenzyl, dibutoxyethyl, and dioctyl phthalate; methylphthalylethyl, butylphthalylbutyl, di(2 ethylhexyl) phenyl, tricrestyl,cresyl diphenyl, tri (beta-chloroethyl), and monocresyl diphenylphosphate; and the polyester plasticizers. Of these, dipropylene glycoldibenzoate is preferred.

Conventional defoamers and preservatives are used to advantage as arefluidifying agents and plasticizers for the starch, such as sodiumnitrate, sodium chloride and calcium nitrate. In addition, the pH isadjusted to about 3 to 9. Preferably, the pH is from 5 to 6.5 for bestcommercial results.

For efiecting the best clean machining properties, it is preferred toalso incorporate in the adhesive a gum selected from the groupconsisting of gum tragacanth, gum karaya, Irish Moss, and mixturesthereof. Such gum can be added in amounts ranging from 0.05 part toabout 5 parts by weight for each100 parts by weight of resin andplasticizer in the adhesive.

Illustrative proportions of the materials and those that are commendedfor best commercial results are shown in the following table:

Within the ranges noted, optimum results are obtained when the ratio ofresin and plasticizer to starch is about 4:1, based on total solids. Theratio can be varied dependent upon the activity of the plasticizer. Themore active the plasticizer, i.e., the greater its softening action 3 onthe resin, the more starch that can be used in proportion of resin.

The invention will be further illustrated by detailed description inconnection with the following specific examples of the practice of it.In these examples and elsewhere herein, proportions are expressed asparts by weight unless stated to the contrary.

EXAMPLE 1 Parts Water 22.68 Gum tragacanth .50 Waxy milo starch 11.00Sodium nitrate 3.20 Sodium hydroxide (18.5%) .40 Vinyl acetateinterpolymer 1 (54.5% total solids) 45.70 Dipropylene glycol dibenzoate13.70 Glycerine 2.30 Phenol .30 Defoamer .22

Inter-polymer of approximately 74 parts vinyl acetate, 24 parts l-ethylhexylacrylate, and 2 parts itaconic acid.

The water, gum tragacanth, waxy milo starch, and sodium nitrate werecombined and heated to 85 C. with agitation for 15 minutes. The mixturewas then cooled to 50 C. and the sodium hydroxide and vinyl acetateinterpolymer added with continued agitation. Agitation was continued asthe dipropylene glycol dibenzoate and remaining components were added,the mixture was adjusted to ambient temperature.

The viscosity of the resultant adhesive was adjusted with slight amountsof water to 180,000 cps. as measured by a Brookfield HVA viscosimeterusing a No. 4 spindle.

The adhesive was stored for 2 months and after that time it was notedthat the product had excellent shelf life in that there was noseparation of the components and the viscosity was stable after thisperiod of time.

The adhesive was then used to adhere paper labels to containers and thefollowing tests were performed:

(1) After aging a group of the labeled containers in a dessicator atrelative humidity and at room temperature for 72 hours, the gluedassembly was torn apart and 100% fiber failure was observed.

(2) The same test as in 1 above was performed on a second group exceptthat the relative humidity was 95%. Again 100% fiber failure wasobserved.

EXAMPLE 2 The adhesive of Example 1 was used to adhere 4" x 6" paperlabels onto polyvinyl chloride containers using a World Super CM-TwoStation Labeler. The containers were fed to the labeler at the rate of82 containers per minute (41 per station) and the machine was run fortwo and one-half hours.

The machining characteristics of the adhesive showed no stringing intransfering from the glue tray to the label; no buildup of adhesive onthe picker plate; excellent initial tack (there was no label slippage);and excellent adhesion to the container. In addition, there was noresidue on equipment parts and when the Water tray was substituted forthe glue tray, the machine ran normally showing the adhesive to beeasily dispersed. In brief, it was an easyclean adhesive.

When the adhesive was completely dry, adhesion tests as set forth inExample 1 showed 100% fiber failure.

EXAMPLE 3 Tests are run using the adhesive of Example 1 to adhere paperlabels to bottles made of polystyrene, polyvinylidene chloride, andpolyacrylics, such as polymethyl methacrylate and copolyrners of acrylicacid and acrylic esters with polyvinyl chloride. In each case there isexcellent adhesion to the plastic and paper (100% fiber failure) withthe labeling machine being easy to clean.

4 EXAMPLE 4 Adhesives were made under the identical conditions set forthin Example 1 with the exception that equal amounts of each of thefollowing starches was in turn used in place of waxy milo starch usedtherein:

(1) Acid modified corn starch (2) Oxidized starch (3) Raw corn starch(4) Raw tapioca starch (5) Tapioca dextrine (6) Corn dextrine (7) Potatodextrine Each adhesive in turn was used to adhere paper labels topolyvinyl chloride surfaces. While all were operative, the adhesives didnot have the excellent tack and machining properties of the adhesive ofExample 1.

The adhesive was compounded as set forth in Example 1 with 3.195 ofwater added to adjust the viscosity to 180,000 cps.

EXAMPLE 6 The method and formulation set forth in Example 1 are followedexcept that equal proportion of an interpolymer of 74.5 parts vinylacetate, 24 parts dioctyl maleate, 0.5 part acrylic acid, and 1 partacrylamide is substituted for the vinyl acetate interpolymer usedtherein. Equally good adhesive and machining properties are obtained.

EXAMPLE 7 The method and formulation of Example 6 are followed exceptthat /2 to 1 /2 parts of each of the polymerizable monomers set forthabove is substituted for the acrylic acid and acrylamide used therein.Suitable adhesives are obtained in each case.

While the instant invention has been described in connection withadhering labels to plastic bottles it will be evident that it isoperative for use in adhering various materials to plastic film membersregardless of the form of the film; i.e., regardless of whether the filmis in the form of bottles, sheets, surface coatings, etc.

It will be understood that it is intended to cover all changes andmodifications of the examples of the inven tion herein chosen for thepurpose of illustration which do not constitute departures from thespirit and scope of the invention.

What is claimed is:

1. A resin adhesive for labelling plastic containers consistingessentially of (1) as the sole resin component from about 20 to about 70parts by Weight of an interpolymer of vinyl acetate with a C C ester ofan acid selected from the group consisting of fumaric, maleic, acrylicacids and mixtures thereof, in the proportion by weight of from 35 to 55parts of ester for each parts of vinyl acetate and 0 to 5% based ontotal weight of interpolymer, of a polymerizable monomer selected fromthe group consisting of ethenoid bond containing carboxylic acids, acidamides, and mixtures thereof; (2) from about 8 to about 12 parts byweight of a starch component selected from the group consisting of waxystarches, hydroxyalkyl starch ethers, acid modified starches, oxidizedstarches, and dextrines; and (3) from about 5 to about 30 parts byweight of a plasticizer for said interpolymer; there being, on a solidsbasis, about four parts of interpolymer and plasticizer combined foreach part of the starch component.

2. A plastic-cellulosic structure comprising a plastic surface havingadhered thereto a cellulosic sheet with the adhesive of claim 1 in curedcondition.

3. A plastic-paper structure comprising a polyvinyl chloride bottle anda paper sheet adhered thereto with the adhesive of claim 1.

4. An adhesive as set forth in claim 1 additionally containing fromabout 0.05 to about 4 parts by weight of a water soluble gum selectedfrom the group consisting of gum tragacanth, gum karaya, Irish moss, andmixtures thereof for each 100 parts by weight of resin and plasti- 20cizer in the adhesive.

5. An adhesive for adhering cellulosic materials to plastic containersconsisting essentially of (1) from about 40 to about 50 parts by weightof an interpolymer of vinyl acetate with 2-ethy1hexyl acrylate anditaconic acid, (2) from about 8 to about 12 parts by weight of a waxymilo starch, and (3) from about to about 15 parts by weight ofdipropylene glycol dibenzoate, there being, on

a solids basis, about four parts of interpolymer and said dibenzoatecombined for each part of the waxy milo starch.

References Cited UNITED STATES PATENTS 2,880,898 4/ 1959 Navikas -l2l5-1.5 3,036,977 5/ 1962 Koch et al.

3,275,589 9/1966 Alexander et a1 26029.6 2,628,948 2/ 1953 Kunze et a1260-17 2,763,578 9/ 1956 Simons.

2,885,374 5/1959 Sweeney.

3,258,443 6/ 1966 Cantor et a1.

3,365,410 1/1968 Wesslau et a1.

OTHER REFERENCES Gelva: Polyvinyl Acetate, Polymers and Copolymers,published by Shawinigan Resins Corp., 1961, pp. 12, 13, 16 and 17 cited.

ROBERT F. BURNETT, Primary Examiner R. H. CRISS, Assistant Examiner US.Cl. X.R.

